In the prior art, electromagnetic vibratory feeders typically have been operated at frequencies obtained directly from power line frequencies, such as at 60 Hz in the United States and generally in North America, and at 50 Hz in Europe, Asia, and other parts of the world. A particular advantage of operating such electromagnetic vibratory feeders at the applicable power line frequency is that the corresponding frequency controls are comparatively simple and cost advantageous, especially for relatively small feeders where the cost of the control mechanism may be a significant portion of the overall feeder cost.
There are various benefits to operating electromagnetic vibratory feeders, however, at frequencies lower than the power line frequency. Because acceleration is a function of the square of the operating frequency, the feeders operating at power line frequencies are subject to high accelerations, which place large demands on the integrity of mechanical structures, significantly adding to equipment costs and reducing the expected equipment lifetime. The requirements for the springs utilized in such electromagnetic vibratory feeders are also determined, among other things, by the frequency of operation; operation at power line frequencies therefore requires a large number of expensive springs that are subject to high stresses and which are difficult to maintain in a stable fashion. Lastly, feed rate is determined by various combinations of feeder amplitude, frequency and feed angle, such that better or more optimal combinations for performance may be obtained at lower operating frequencies.
Prior art solutions for providing low frequency controls typically involve complicated electronic circuitry, such as in power inverters or other complex means of control. While such complicated controls may be economically feasible for large feeders, such controls are prohibitively expensive for use in smaller feeders. As a consequence, a need remains for an apparatus and system to provide a means to control, at low cost, the operating frequency of an electromagnetic vibratory feeder at a submultiple (or fraction) of the power line frequency, without sacrificing output control.